Are the Qlik Sense services up and running? => Try to start and restart them to see if it comes back up and running. (You might need to wait a few minutes before the services become operational)
Are you using the correct URL to access the Qlik Sense Management (QMC) and HUB? => You can try to access them connected remotely to the Qlik Sense Server by accessing the URL https://localhost/qmc or https://localhost/hub. If this works you might have a DNS and/or a network issue.
The issue has started occurring after a fresh installation or an upgrade of the product without having worked before
If after checking the above points you still experience issues, you need to know that to start properly, the Qlik Sense Management Console will need to have few services properly working:
The Qlik Sense Repository Database
The Qlik Sense Repository Service
The Qlik Sense Dispather
The Qlik Sense Proxy
To verify if those services are actually functioning correctly, you will need to check their logs. Start by looking into the Qlik Sense Repository logs stored by default in C:\Programdata\Qlik\Sense\Log\Repository\Trace\Servername_System_Repository.txt. (You might want to restart the services before looking into this log to get fresh information)
If the Qlik Sense Repository Database and Service starts correctly you are basically looking at the following string in this logs (It might take few minute to initialize after a service restart) Startup phase completed
If you do not find this string in the logs, then you will likely need to search for the first ERROR and/or WARN showing in this logs. You can then grab the content of the message and search it in our knowledge base
However if the you find this string in the logs, the next step if to check the Qlik Sense Proxy logs stored by default in C:\Programdata\Qlik\Sense\Log\Proxy\Trace\Servername_System_Proxy.txt Once again we would recommend to restart the Qlik Sense Proxy Service before looking into the logs to get fresh information.
In this log you might see few errors at the beginning saying When contacting https://localhost:4242/ No connection could be made because the target machine actively refused it 127.0.0.1:4242 Could not contact local repository to retrieve local server node configuration No connection could be made because the target machine actively refused it 127.0.0.1:4242
Those will be expected since the Qlik Sense Proxy service will try to connect to the Qlik Sense Repository Service, so as long as the startup phase is not completed for the Qlik Sense Repository service you will keep getting those events in the logs. Basically if the Qlik Sense Proxy service is starting correctly you should expect the following event in the logs:
Proxy is running
As for the Qlik Sense Repository if you do not find this string in the logs, then you will likely need to search for the first ERROR and/or WARN showing in this logs. You can then grab the content of the message and search it in our knowledge base.
E.g. Here is an example of the types of error you can get in the Qlik Sense logs:
Proxy will NOT be listening to port 443, likely bound by another process An attempt was made to access a socket in a way forbidden by its access permissions.
The above steps should help you to investigate the root cause of your issue for this scenario.
The issue occurs on a random basis from time to time
In the following scenario we are more looking into an environment issue such as network connectivity, resource overload, ... The first step would be to check the Qlik Sense Repository Service and Proxy logs as described above to find any relevant ERROR and/or WARN that could explain the root cause.
Then you can start looking into the Windows Event logs (Application and System) to find any problem at a system level around the time you are getting this issue.
Below are common causes/events that you could find in those logs: